The present studies are designed to investigate the effects of in utero diethylstilbestrol exposure on the reproductive system of adult men. Three basic types of adverse effects will be looked for: anatomical abnormalities, abnormalities of the seminal fluid analyses and impaired fertility potential. Anatomic abnormalities will be sought by physical examination, with particular attention being paid to examination of the body habitus, testicles, penis, prostate gland, and epedidymis. Seminal fluid analyses will be performed three times on each subject to ascertain whether there exists any specific abnormality in sperm concentration, motility or morphology. Fertility potential will be evaluated by the Sperm Penetration Assay (SPA), a recently-developed procedure which determines the ability of a particular sample of human sperm to penetrate zona-free hamster eggs. Data from our Reproductive Genetics Laboratory and others indicate that this is the most reliable available procedure for the prediction of male fertility, as it is the only known measure of sperm function. Correlations will be sought among specific manifestations of the three basic types of abnormality, as well as among specific abnormalities and dosage and gestational timing of diethylstilbestrol administration.